Foreign ministers from the G7 group of rich nations backed giving more aid and weapons to Ukraine as they met today in what Germany called a "powerful sign of unity" to deepen Russia's global isolation for invading its neighbour.

The European Union's foreign policy chief Josep Borrell announced a further €500 million worth of military support that should be approved next week by EU members, and expressed confidence that the bloc will agree an embargo on Russian oil.

British Foreign Minister Liz Truss announced new sanctions targeting Russian President Vladimir Putin's financial network and inner circle, including his ex-wife and cousins, and also called for ramping up weapons supplies to Ukraine.

The annual meeting running until tomorrow brings together top diplomats from Britain, Canada, Germany, France, Italy, Japan, the United States and the EU to a 400-year-old castle estate in the Baltic Sea resort of Weissenhaus.

It follows promises by G7 leaders last weekend to ban or phase out buying Russian oil.

The event, which the foreign ministers of Ukraine and Moldova attended, also spotlighted food security concerns and fears that the war in Ukraine could spill over into its smaller neighbour Moldova.

Moldova's foreign minister said in an interview that some forces in the breakaway region of Transdniestria were bent on sowing instability but that his government wanted to solve the issue through diplomacy.

The G7 talks will defy Russian attempts to split the world over Ukraine, German Foreign Minister Annalena Baerbock said.

"Never since the end of the Cold War have we G7 partners been more profoundly challenged. Never before have we stood more united," she said on Twitter.

Vladimir Putin had no intention of stopping the war, Mr Borrell said, adding that the new EU military support would be for heavy weapons such as tanks and artillery and take the bloc's aid to about €2 billion.

"(It will be) more pressure on Russia with economic sanctions and continuing the international isolation of Russia and countering misinformation," he said.

Speaking to reporters on the sidelines of the meeting, Ukraine Foreign Minister Dmytro Kuleba challenged the EU to impose the oil embargo, saying Vladimir Putin would celebrate if the proposal fell through.

Ukraine's neighbour Hungary has opposed the plan, which requires unanimity to pass.

"We do not interfere in their discussion, but it's acritical moment when we will see whether EU unity will continue to exist or whether it will be broken," he said.

Ukraine's Foreign Minister Dmytro Kuleba speaking to journalists at the G7 today

Mr Kuleba called on allies to seize Russian assets to finance the rebuilding of Ukraine, a proposal backed by Germany's Finance Minister Christian Lindner in an interview published by Germany weekly Der Spiegel today.

Germany this weekend separately will host ministers from NATO, as Sweden and Finland gear up to apply for membership of the transatlantic alliance, drawing threats of retaliation from Moscow and objections from NATO member Turkey.

Moldova alarm

The war in Ukraine has sent global prices for grains, cooking oils, fuel and fertilizer soaring, with United Nations agencies warning that the price hikes will worsen a food crisis in Africa in particular.

Russia's invasion has disrupted shipping in the Black Sea, a major route for grains and other commodities, throttling exports.

Agriculture ministers at the G7 today

Diplomatic sources said the aim was for the seven countries to organise themselves better to find quick and efficient answers to the food crisis. With Russia blockading Ukrainian ports, efforts will likely centre on speeding up shipments of produce on goods trains to the rest of Europe.

Moldova is struggling to cope with the refugee flow from Ukraine and incidents involving pro-Russian separatists in Transdniestria have raised alarm.

"They are limited, but want to play games stoking up tensions, provoking, (making) the population of Transdniestria hysterical and making nervous the population of Moldova," Foreign Minister Nicu Popescu said.

"There are internal forces that want to destabilise this region and bring war closer to our homes. We are working to make sure this is not happening."